351w intake install:exhaust restrictors? yes or no?
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Lead Driver
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From: Midwest
351w intake install:exhaust restrictors? yes or no?
I am putting a wieand intake manifold on my 78 f100 with a 85 351w HO. The intake gasket set came with exhaust cross over restrictors. what is the purpose of exhaust going thru the intake manifold? is this for EGR purposes? I do not have to worry about emissions,and I am running with out EGR. if I put these restrictors in,will it affect the running of the engine good or bad? thanks for any help,Ben 
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The crossover works in conjunction with a valve located at the collector of the driver's side stock exhaust manifold. When cold the valve shuts and forces exhaust across the manifold to heat things up quicker. On a very high performance motor people usually block them off, mostly because the valve constricts the exhaust. With no valve there is no need for the crossover. On a daily driver, especially in a cold climate, you may want the quicker engine warm up.
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Lead Driver
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From: Midwest
I am not using my stock 85 exhaust manifolds,I am using the exhaust manifolds off the 302 that was stock in the truck,and they don't have that valve. I am going to headers soon. so i should be ok to block it off,right? would it hurt anything not to block it off if i am not going to use it with the exhaust on it now,or the headers in the future? on edit,thanks for the reply,netfly,i didn't catch the part of your post until now that said "if there is no valve,there is no need for a cross over" that would be the answer I am looking for 
Last edited by cjben; Mar 11, 2005 at 08:30 PM.
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From: Ocala, Florida
If you block off the crossover you may end up with icing, the exhaust gasses that flow through help prevent it (carb icing). You can try it, but if the engine runs lousy, you may have to do the job all over again and remove the crossover blocks.
I left them out when I did my manifold and there are no problems.
I had a friend who put the crossover block in and regretted it. He had to do the job over because his carburetor kept icing up.
I left them out when I did my manifold and there are no problems.
I had a friend who put the crossover block in and regretted it. He had to do the job over because his carburetor kept icing up.
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I agree with mako, you may want to leave them off if its a daily driver, otherwise expect 20 min. for what would normally be a 5 min. warm up. While driving a cold engine longer icing is a concern. It would need a manual choke for sure. Without the exaust valve you will still get some warming if you leave them off. Exhaust heat will find its way there, just not as fast as when its forced there with one exhaust pipe blocked. Once the engine is warm the extra heat isn't helpful, but won't slow you down much either. All in all I'd leave them off for most street cars.
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